2. • Zika virus ( ZKV ) is a mosquito-borne flavivirus first isolated in Uganda from a sentinel monkey
in the Ziika forest in 1947.
• Sporadic outbreaks in tropical Asia and Southeast Asia, large outbreak in Micronesia in 2007 and
in French Polynesia in 2014, with evidence of transplacental transmission in pregnant women.
• An outbreak of skin rash in Northeastern Brazil was found to be caused by Zika.
• From 2007 to 2016, the virus spread eastward, across the Pacific ocean to the Americas leading to
the 2015-16 Zika virus epidemic.
• Spread by daytime-active Aedes mosquitos, such as A . aegypti and A . Albopictus.
• Zika fever disease, No or mild symptoms, similar to Dengue, Yellow fever, Japanese encephalitis,
and West Nile viruses.
3. Properties & Structure of Zika virus
Genome architecture : + ss RNA, Non-segmented
Balti. Class : IV
Family : Flaviviridae
Genus : Flavivirus
Species : Zika virus
Virion : 40 nm, surface projections roughly 5-10 nm
Nucleocapsid : 25-30 nm, surrounded by a host-membrane derived lipid bilayer
Enveloped
Icosahedral
Contains envelope proteins E and M
10794 bases long with two non-coding regions flanking regions known as the 5’ NCR and the 3’ NCR
BSL - 2
4.
5.
6. Replication
1. Attachment of the viral envelope protein E to host receptors mediates internalization
into the host cell by apoptotic mimicry
2. Fusion of virus membrane with host endosomal membrane. RNA genome is released into the cytoplasm
3. The positive-sense genomic ss RNA is translated into a polyprotein, which is cleaved into
all structural and non structural proteins ( to yield he replication proteins )
4. Replication takes place at the surface of endoplasmic reticulum in cytoplasmic viral factories.
A dsRNA genome is synthesized from the genomic ss RNA(+)
5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ss RNA(+) genomes
6. Virus assembly occurs at the endoplasmic reticulum. The virion buds at the endoplasmic reticulum
and is transported to the Golgi apparatus
7. The pr M protein is cleaved in the Golgi, thereby maturing the virion which is fusion competent
8. Release of new virions by exocytosis
7.
8. Pathogenicity and infection in human
• Zika virus infection is usually mild and self-limiting.
Vertical transmission :
1. Across the placenta
2. In the breast milk
3. Delivery process
– Severe consequence of vertical in utero transmission
is fetal/newborn microcephaly
– Transfusion transmission
– Sexual transmission
Illness is usually mild and death is rare
About 1 – 5 people infected will become ill
Symptoms normally last 2 – 7 days
15. Diagnosis :
Samples : • Blood, Urine, Semen, CSF, and other body fluid
RT real time PCR for the qualitative detection of RNA in human plasma, serum or urine
Ultrasound scanning for detection of microcephaly in pregnant women
Plaque reduction neutralization test ( PRNT ) for zika virus induced antibodies
The NS1-based ELISA for zika IgG and IgM antibodies
IIFT based on virus-infected cells for ZIKA antibodies
The NS-1 – based Anti-Zika virus ELISA for analyse anti-ZIKA antibodies of class IgA
EURO Real Time PCR Zika virus test for viral RNA in the early phase of a Zika virus infection
16. Treatment :
No specific antiviral treatment for the Zika virus exists
Supportive treatments such as rest, fluids and medication
for pain relief such as acetaminophen ( Tylenol )
No aspirin
17. Vaccine :
DNA – based vaccines ( NIH )
Inactivated vaccines
Live attenuated
Chimeric vaccines
18. Prevention and control
Remove mosquito breeding sites
Avoid mosquito contact
Use insect repellent regularly
Wear long sleeves and pants
Wear light-colored clothing
Use condoms during sex to prevent the spread of Zika
